There is an increasing need for accurate, fast and low cost assays in the fields of in-vitro diagnostics (IVD) and especially in the field of Point of Care (POC) diagnostics. Nucleic Acid aptamers have been considered in recent years for use in diagnostic applications.
Aptamers are oligonucleic acid molecules which are obtained by in vitro selection methods such as Synthetic Evolution of Ligands by Exponential Enrichment (SELEX).
Aptamers have a specific binding to a target molecule such as a protein with high affinities in the nanomolar and subnanomolar range. For example, aptamers against vascular endothelial growth factor and keratinocyte growth factor show affinities of 100 pM and of 1 pM, respectively (L R Paborsky et al., “The Single-Stranded DNA Aptamer-Binding Site of Human Thrombin” J. of Biol. Chem. 268 (1993): 808-811). In addition, aptamers can bind small molecules like ATP (M Sassanfar and J W Szostak, “An RNA Motif That Binds ATP” Nature 364 (1993): 550-553).
In recent years, aptamers have been studied as therapeutic tools both for treatment and for prevention, with the first aptamer-based drug recently approved by the U.S. FDA in treatment for age-related macular degeneration (AMD).
Several aptamer-based biodetection approaches have been reported in which aptamers were labeled with molecules such as redox probes, fluorescent dyes, or nanocrystals as an integral part of signal transduction (Mir M, and Katakis I. Aptamers as elements of bioelectronic devices. Mol. Biosyst. 3 (2007): 620-622; Levy, M; Cater, S F; Ellington, A D. Quantum-dot aptamer beacons for the detection of proteins. Chembiochem. 6 (2005):2163-2166). In addition, researchers have recently taken advantage of PCR to amplify DNA aptamers for sensitive detection of protein targets.
In addition, in the past several years there was a growing use of aptamers as chemical antibodies (William James. Aptamers. In Encyclopedia of Analytical Chemistry. R. A. Meyers (2000) 4848-4871 Ó John Wiley & Sons Ltd; Pai S S, Ellington A D, Using RNA aptamers and the proximity ligation assay for the detection of cell surface antigens. Methods Mol. Biol. 504 (2009): 385-398).
Patent application, U.S. Pat. No. 6,458,543 describes a nucleic acid ligand “biochip”, consisting of a solid support to which one or more specific nucleic acid ligand is attached in a spatially defined manner, enabling the specific binding to a target molecule, if present, in a test mixture.
WO 2007/117444 describes methods for diagnosing and staging diseases by detecting and/or measuring proteins associated with certain clinical conditions using a plurality of aptamers that recognize oligopeptide epitopes on a target protein.
WO 01/79562 describes a novel aptamer based two-site binding sandwich assay, employing nucleic acid ligands as capture and/or reporter molecules.
Mir and Katakis (Mir M, and Katakis I. Aptamers as elements of bioelectronic devices. Mol. Biosyst. 3 (2007):620-622) describe an aptamer based-assay having sensitivity of detection in the range of 106-1012 molecules.